Revisiting Disorder in High-Temperature Superconductors

It is known that the crystal structures of copper-oxide superconductors are rather disordered. We attempt to understand various disorder-related electronic properties in these materials using exact real-space numerical methods. We calculate the quasiparticle density of states (DOS) using various models of disorder and find that a finite DOS arises at the Fermi energy from smooth disorder due to off-plane dopants, and show that a residual linear-T contribution to the specific heat naturally results at realistic doping levels. We also find that smooth disorder has a more muted effect on the localization of quasiparticles than pointlike disorder. We model quasiparticle scattering interference as measured in scanning tunneling spectroscopy (STS) and find that the peaks seen in experiment are far better defined than according to our simulations, indicating that a more microscopic modeling of the tunneling process is needed to fully reproduce experimental results. We also study the effects on the STS spectra coming from the interplay between disorder and electronic self-energies parametrizing the effects of interactions.